When we analyze Food and Drug Administration data, however, we find something surprising and possibly heartening: Many people underestimate how many calories nutritionists estimate they should consume each day.

Know Your Caloric Benchmark

One of the most important things to know during the often food-centric holidays if you want to avoid gaining weight is how many calories you can consume each day.

On most packages of food you will see a box listing nutritional facts. The majority of these boxes show values for fat, cholesterol, sodium, and other nutritional information based on a 2,000-calorie daily diet. Although the label is currently undergoing a redesign, the 2,000 daily calorie figure will not change.

Based on these labels, consumers often think that 2,000 calories is the recommended amount they should consume each day. Yet it is wrong for most people.

Caloric Breakdown

The government separates adults aged 18 and over into many categories based on age and how active a person is each day.

In general, the younger and more energetic you are, the more calories you can consume. For example, active 18-year-old men need 3,200 calories per day, while women with the same characteristics need only 2,400. Sedentary men in their 50s require 2,200 calories, while sedentary women in the same age group need just 1,600 calories.

At the extreme end, elite athletes like swimmer Michael Phelps consume up to 12,000 calories during training periods.

In the government’s table, some categories cover only a single year, like being 18 years old; some cover a five-year range, like 36 to 40; and others cover many years, like 76 and up. On the whole, however, fewer than 20 percent of the categories have recommendations for exactly 2,000 calories, a standard that appears to have been chosen because it was in the general ballpark for many people and, well, it was easy to use.

Professional athletes like Michael Phelps eat up to 12,000 calories a day while in training.

Few People Know Accurately

One of the more interesting things we noticed while doing our research is that most people don’t know how many calories they can consume without gaining weight.

It is hard to know whether you can eat another holiday treat if you don’t know your daily calorie recommendation. Or, for that matter, how many calories are in that delicious-looking ginger snap — about 28 — or slice of apple pie — about 300. (Editors note: Roughly 71 ginger snaps equal 2,000 calories, the standard guideline for how many calories you should consume every day.)

The Federal Drug Administration periodically runs nutritional surveys with randomly selected people aged 18 and over in the US. The most recent survey was given to more than 1,200 individuals in 2014. In that survey, the FDA asked respondents: “About how many calories do you think a man (or woman) of your age and physical activity needs to consume a day to maintain your current weight?”

Using their answers and their demographic details, it is possible to calculate how close people’s estimates are to the actual levels recommended by the government. Even without knowing how much respondents exercised, the answers were stunning.

Forty percent of respondents thought people like themselves should be consuming fewer than 1,500 calories per day, which is less than the lowest caloric recommendation for any age and activity group in the US dietary guidelines. Another 10 percent or so offered a figure higher than 1,500 but still underestimated the correct value for someone of their age and gender who lives a sedentary life.

An additional five percent overestimated their recommendation, going even higher than the suggestion for an active person of their age and gender. And 10 percent of respondents said they didn’t know how many calories a person like him or herself should consume. The remaining 35 percent provided a figure that was exactly what the FDA recommended or quite close.

In other words, about two-thirds of respondents didn’t know how many calories they should consume a day — and most of those assumed it’s lower than what it actually is.

That so many adults in the US have mistaken perceptions is important because it is hard to lose or gain weight if you don’t know how much you should eat. People who don’t know their caloric target cannot hit it.